In this research aluminum trihydrate (ATH) and magnesium dihydrate (MDH) used to improve thermal conductivity of high density polyethylene (HDPE). ATH and MDH are flame retardant materials that extensively used in wire and cable industries. In this research effect of particle and concentration of filler on thermal conductivity of HDPE /ATH/MDH were investigated. Results show by increasing concentration of filler up to 60% volume thermal conductivity of HDPE composites were increased by 300% rather than HDPE alone. Experimental results were compared with different models. The best model to fit the experimental result is mean geometry model. Results also show that with increasing particle size of filler (ATH/MDH) thermal conductivity of composites were increased. Mechanical, flammability and flow behavior of composites also were investigated. Results shows that with increasing concentration of filler (ATH/MDH) up to 60% by volume, flammability were in the range of flammability test (UL-94). Melt flow index (MFI) of composite with increasing concentration of filler were decrease.
